Electric glassmaking furnace



April 1968 J. M. Y. LE CLERC DE BUSSY 3,376,373

ELECTRIC GLASSMAKING FURNACE Filed March 10, 1965 United States Patent 3,376,373 ELECTRXC GLASSMAKTNG FURNACE Jacques Marie Yves le Clerc d'e Bossy, Paris, France, as-

signor to Verreries Pochet et du Courval, Paris, France. a French body corporate Filed Mar. 10, 1965, Ser. No. 438,574

Claims priority, application France, Mar. 17, 1964,

3 Claims. (Cl. 13--6) In American Patent No. 3,147,328 there is described an electric glassmaking furnace comprising a refining device disposed inside the trough at the hottest region of this chamber, this device comprising means for withdrawing in the course of the continuous pouring, a portion of the molten glass in this region and thus removing it from the large movements due to the convection currents prevailing in this chamber, means for submitting this portion to a rapid rise of temperature so as to diminish its viscosity and to increase the size of the bubbles which are thus separated from the fine glass, means for dis-charging the fine glass thus obtained, to the exterior as its production proceeds, and means for returning to the bath inside the furnace the bubbles t-hus separated.

The present invention has as its object modifications and improvements applied to this furnace.

In particular, in an embodiment of the furnace according to the abovementioned patent the refining device comprises two horizontal discs with an approximately plane or conical surface, brought nearer towards one another at least at their edges, the spacing between the discs communicating with one or more escape orifices for the bubbles and with an extraction device for the fine glass; the escape orifice for the bubbles communicates with the interior of the trough, and the extraction device for the fine glass communicates with the exterior of the trough; the means which enable the portion of the withdrawn glass to be subjected to a rapid rise of temperature, consist of a source of electric current, the terminals of which are connected respectively to the two discs of said device.

The furnace according to the present invention differs from this embodiment by modifications which result from studies and experiments aimed at further improving the yield of the furnace and of simplifying its construction.

A first series of experiments has shown that it was possible to suppress the current circulating between the discs, by varying the voltage at the terminals of the lateral electrodes in a manner such as to bring them nearer to central electrode, in other words, operating with the same power but with a lower voltage and, consequently, with a higher intensity, which has the effect of overheating the central part of the furnace indirectly and of thus obtaining a glass which is sutficiently fluid so that the separation of the bubbles can be effected.

It is thus possible to dispense with the two rods for feeding the current, connected to the upper and lower discs respectively; the upper disc can simply be placed upon the lower disc, with the interposition of molybdenum wedges between the two discs.

On the other hand, it has been found that it is possible to remove, at least partially, a portion of the glass to the convection currents prevailing in the chamber of the furnace, using a single disc of large diameter; the glass, confined between the edge of the disc and the electrodes, is heated, which facilitates the ascent of the hubbles. The glass is always drawn off in the centre of the disc, and there is a conical zone free of bubbles, provided that care is taken to maintain the discharge of withdrawn glass below a certain limit.

Finally, it has been found that this discharge could be increased by avoiding the formation of air eddies above 3,376,373 Patented Apr. 2, 1968 allows an increase of the discharge of withdrawn glass;

has a surface which is suitable for the use of lateral electrodes;

allows a decrease in the diameter of the refining member for a given discharge of glass.

The furnace is thus considerably simplified, and its parts have a resistance to wear which is particularly beneficial.

The invention thus provides an electric glassmaking furnace of the type described in American Patent No. 3,147,328 which furnace is characterized especially in that the refining device comprises a single element disposed between the electrodes, this element itself not being connected to any source of voltage.

According to another feature of the invention, this element has the shape of a cup or bowl, its concavity being directed upwards, this bowl being supported by the hollow rod which constitutes the passage for withdrawing the fine glass.

Other features will be apparent in the following description of an embodiment, shown and described by way of example.

In the accompanying drawing:

FIG. 1 is an elevation view, in section, of the refining device according to the invention and of one of the electrodes;

FIG. 2 is a plan view of the refining device and of the three electrodes.

According to this embodiment, the refining device comprises a single refining element 101 supported by the rod 27 pierced by a passage 28 for the extraction of fine glass. These parts 101, 27, 28 are preferably of molybdenum. They are centered with respect to the three melting electrodes 11a, 11b, He, supported respectively by conducting rods 9a, 9b, 90. These electrodes and rods are like wise of molybdenum; the electrodes 11a, 11b, 110 have concave cylindrical faces 12a, 12b, 12c directed towards the axis of symmetry XX of the device.

The element 101 has the shape of a cup with an upwardly directed concavity, or preferably, the shape of a bowl with a spherical or, as shown, a conical bottom.

For certain types of glass which are little sensitive to reduction and particularly diificult to refine, it is preferred to fill the bowl with crushed molybdenum pieces 102 of, for example, of 5 to 10 mm; these regulate the absorption of the glass above the level of the bowl, and enhance the collecting of the bubbles in the numberous battles thus formed, which fact enhances the ascent of these bubbles.

The electrodes 9a to can be of partially fused pressed molybdenum, such as described in the patent application for Process for Manufacturing Electrodes for Furnaces for the Electric Melting of Glassware and Electrode Obtained by Carrying Out Said Process, Ser. No. 439,391, filed Mar. 12, 1965.

The invention is not limited to the embodiment as illustrated and described, which has been chosen by way of example only.

Having now described my invention what I claim as new and desired to secure by Letters Patent is:

1. An electric glassmaking furnace comprising a trough having a chamber, a refining device disposed in the trough in the hottest region of the chamber, said device comprising means for withdrawing in the course of the continuous pouring a portion of the molten glass in said region and thus removing it from the large movements due to the convection currents prevailing in the chamber, means for subjecting said portion to a rapid rise of temperature so as to diminish the viscosity and increase the size of the bubbles which are thus separated from the fine glass, means for discharging the fine glass thus obtained to the exterior as production thereof proceeds, and means for returning to the bath inside the furnace the thus-separated bubbles, said refining device comprising a single element disposed between electrodes, said element being unconnected to any source of voltage.

2. Furnace as claimed in claim 1, wherein said element has the shape of a cup and a concavity which is upwardly directed, said cup being supported on a hollow rod which constitutes the passage for Withdrawing the fine glass.

3. Furnace as claimed in claim 2, wherein said element is at least partially filled with molybdenum pieces,

References Cited UNITED STATES PATENTS 3,147,328 9/1964 Le Clerc De Bussy 13-6 10 BERNARD A. G-ILHEA-NY, Primary Examiner.

H. B. GI'LSON, Assistant Examiner. 

1. AN ELECTRIC GLASSMAKING FURNACE COMPRISING A TROUGH HAVING A CHAMBER, A REFINING DEVICE DISPOSED IN THE TROUGH IN THE HOTTEST REGION OF THE CHAMBER, SAID DEVICE COMPRISING MEANS FOR WITHDRAWING IN THE COURSE OF THE CONTINUOUS POURING A PORTION OF THE MOLTEN GLASS IN SAID REGION AND THUS REMOVING IT FROM THE LARGE MOVEMENTS DUE TO THE CONVECTION CURRENTS PREVAILING IN THE CHAMBER, MEANS FOR SUBJECTING SAID PORTION TO A RAPID RISE OF TEMPERATURE SO AS TO DIMINISH THE VISCOSITY AND INCREASE THE SIZE OF THE BUBBLES WHICH ARE THUS SEPARATED FROM THE FINE GLASS, MEANS FOR DISCHARGING THE FINE GLASS THUS OBTAINED TO THE EXTERIOR AS PRODUCTION THEREOF PROCEEDS, AND MEANS FOR RETURNING TO THE BATH INSIDE THE FURNACE THE THUS-SEPARATED BUBBLES, SAID REFINING DEVICE COMPRISING A SINGLE ELEMENT DISPOSED BETWEEN ELECTRODES, SAID ELEMENT BEING UNCONNECTED TO ANY SOURCE OF VOLTAGE. 